sources and fate of nutrients. Congress amended the Clean 

 Water Act in 1987 to provide for a comprehensive assessment 

 of pollution problems in the Clark Fork-Lake Pend Oreille 

 Basin. 



An interagency committee consisting of representatives 

 from Montana, Idaho, Washington, and EPA Regions VIII and X 

 has outlined a plan to expand studies of nutrients and 

 eutrophication in the basin. Details of these plans are 

 provided in Chapter 5. 



NONPOINT SOURCE POLLUTION 



Introduction 



Nonpoint source pollution (NPS) of surface and ground 

 water is derived from activities such as agriculture, 

 silviculture, mining, construction, land disposal, hydro- 

 modification, and others. The sources are diffuse, and 

 contamination usually results from overland runoff, percolat- 

 ion, precipitation, or atmospheric deposition rather than 

 from a discharge at a specific, single location (EPA 1987c) . 



Nonpoint source pollution is a major problem in the 

 Clark Fork Basin, both in the tributaries and along the 

 mainstem. The basin has a multitude of pollution sources 

 because its economic base is rooted in agriculture, timber 

 harvesting, mining, and hydropower production. However, 

 because nonpoint sources of pollution are diffuse and can 

 originate from large land areas, identifying and quantifying 

 their effects are difficult. Effective control of NPS 

 remains one of the most challenging issues facing resource 

 managers in the Clark Fork Basins 



General information regarding nonpoint source pollution 

 is provided in Table 3-19. Sediments resulting from erosion 

 are typically the most widespread nonpoint pollutant. In 

 many areas, agricultural practices are the most common cause 

 of water quality problems from nonpoint sources (EPA 1985b) . 



Oftentimes, multiple activities in a watershed con- 

 tribute the same nonpoint pollutant, resulting in cumulative 

 effects on water bodies. Control programs are complicated by 

 the variety of pollution sources and multiple ownership 

 patterns that exist in a given watershed. 



Best Management Practices (BMPs) are important tools in 

 the prevention and control of nonpoint source pollution. 

 BMPs are methods, measures, procedures, or practices used to 

 control or reduce nonpoint source pollution. BMPs can be 

 structural or nonstructural controls or operations and 



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